is it still not possible to delete folders in the file browser?
No. This is still not possible as of 2.73. 

See this thread on the bf-comitters mailing list for some discussion on why this is. 

If I understand correctly, the required capability was recently added to blender's internal delete function, so AFAIK it's more or less a matter of creating a higher level recursive delete operator. Perhaps It'll be here soon.